The invention relates to a low voltage switch gear with a bimetallic tripping device, in particular a motor protection switch or a power switch.
1. State of the Art
Such switch gears are to be calibrated by the manufacture with respect to the bimetallic tripping device. The tolerances present between the bimetallic strips of the individual phases are to be balanced amongst each other, are to be balanced between the bi-metals and the flip point of the releasing jack system as well as to be balanced with respect to a required empty path of the bi-metals. Such a bi-metal tripping device and a corresponding pawl or jack system are described in detail in the German printed patent document DE 4202049. The calibration process is in general performed such that after a measurement technical capturing of the release paths of the bi-metal device group and of the flip point of the jack system, a bridge system to be actuated by the bending out of the bi-metals is balanced with respect to that punchings for the engagement of the bi-metals are performed exactly in that measure corresponding to the above recited measurement technical capturing such that the above recited tolerances are balanced out as far as possible after completing of the bi-metal device group by the bridge system. This process of the balancing of the bridge system is designated in the following as calibrating by punching. By performing calibration by punching recited tolerances are in fact balanced, however, the together assembly according to U.S. Pat. No. 5.909,164 in a lower casing part of the switch gear together with the contact system and the drive system of a loosely supported bimetallic device group, of the bridge system, and of an upper casing part required for the support and covering of these parts entail the associated danger not to be underestimated, that new tolerances are generated between the bi-metal group, the bridge system and the pawl system.
2. Presentation of the Invention
Therefore it is an object of the invention to eliminate tolerances between bi-metal tripping device and jack system generated during assembly of the switch gear.
The object is accomplished according to the present invention by the characterizing features of the independent claims starting from a low voltage switch gear. It is now possible based on an opening furnished in the casing to capture the bi-metal device group and the pawl system in the finally incorporated state for the purpose of calibration of the still not incorporated bridge system by a measurement technology, then to assemble the correspondingly calibrated bridge system, and finally to close the opening by the protective cover. All tolerances concerning the bi-metal tripping device are captured advantageously over the complete production and assembly chain during calibration of the bridge system. After the calibration only one device group, namely the bridge system, is to be incorporated with the switch gear according to the present invention in contrast to switch gear of the state of the art. An advantageous further development of the invention comprises that the protective cover is lockingly attached on the casing.